阅读说明：本技术 一种电解铝阳极钢爪用防腐防氧化涂层材料及其制备方法 (Anticorrosive and anti-oxidation coating material for electrolytic aluminum anode steel claw and preparation method thereof ) 是由 芦亚楠 黄强 芦永军 韩飞 张树奇 沈红民 王银娟 于 2021-06-21 设计创作，主要内容包括：本发明公开了一种电解铝阳极钢爪用防腐防氧化涂层材料及其制备方法,其原料按质量百分含量,包括40-70％α-Al-(2)O-(3)、0-30％γ-Al-(2)O-(3)(优选5-30％)、2-7％硅酸铝纤维和20-30％水玻璃。本发明提供的电解铝阳极钢爪用防腐防氧化涂层材料的原料中最大限度地使用各种氧化铝,只少量含有其它元素,可防止其它元素进入电解液,从而避免对铝制品质量的影响。本发明涂层材料结构致密,可减少腐蚀性气体的渗透量,能明显降低电极的腐蚀速率,抗腐蚀能力强,耐磨性能好。本发明涂层材料的延展性增强,适合高温环境,且在高温环境中使用时不易开裂脱落。(The invention discloses an anticorrosive and anti-oxidation coating material for electrolytic aluminum anode steel claws and a preparation method thereof, wherein the raw materials comprise 40-70% of alpha-Al in percentage by mass 2 O 3 、0‑30％γ‑Al 2 O 3 (preferably 5-30%), 2-7% aluminium silicate fibres and 20-30% water glass. The raw materials of the anticorrosive and anti-oxidation coating material for the electrolytic aluminum anode steel claw provided by the invention use various aluminum oxides to the maximum extent, only contain a small amount of other elements, and can prevent the other elements from entering into electrolyte, thereby avoiding the influence on the quality of aluminum products. The coating material of the invention has compact structure, can reduce the permeation quantity of corrosive gas, can obviously reduce the corrosion rate of the electrode, and has strong corrosion resistance and good wear resistance. The ductility of the coating material is enhanced, and the coating material is suitable for high-temperature environmentAnd is not easy to crack and fall off when used in a high-temperature environment.)

1. An anticorrosion and antioxidizing coating for the anode steel claw of electrolytic aluminium is prepared from alpha-Al (40-70 wt.%)₂O₃、0-30％γ-Al₂O₃(preferably 5-30%), 2-7% aluminium silicate fibres and 20-30% water glass.

2. The coating material of claim 1, wherein the raw material preferably comprises, in mass percent, 45-55% α -Al₂O₃、15-25％γ-Al₂O₃3-6% of aluminum silicate fiber and 22-27% of water glass.

3. The coating material of claim 1, wherein the raw material comprises 48-52% α -Al by mass₂O₃、18-22％γ-Al₂O₃4-6% of aluminum silicate fiber and 24-26% of water glass.

4. The coating material of any of claims 1-3, wherein α -Al₂O₃Is in the form of powder, and has a particle size of 150-325 meshes, preferably 200 meshes.

5. The coating material of any of claims 1-4, wherein γ -Al₂O₃Is in powder form, and the granularity is less than or equal to 0.043 mm.

6. The coating material of any of claims 1 to 5, wherein the aluminosilicate fibers have a fiber length of 2mm or less and a fiber cross-sectional diameter of 0.03mm or less, and wherein the fibers contain Al₂O₃The content is more than 50 percent.

7. The coating material according to any one of claims 1 to 6, wherein the coating material is selected from the group consisting ofThe sodium silicate is powder with granularity less than or equal to 0.1mm and is selected from sodium silicate and/or potassium silicate and Na in the sodium silicate₂O·nSiO₂＞95％。

8. The coating material of claim 7, wherein the mass ratio of the sodium water glass to the potassium water glass is (3-5): 1.

9. the coating material of any of claims 1-8, wherein α -Al₂O₃、γ-Al₂O₃The water content of the aluminum silicate fiber and the water glass is less than 0.3 wt%.

10. A method for producing a coating material according to any one of claims 1 to 9, characterized in that the coating material is made of para- α -Al in mass percent₂O₃、γ-Al₂O₃Weighing the aluminum silicate fibers and the water glass, and then uniformly mixing to obtain the coating material.

Technical Field

The invention relates to the technical field of electrolytic aluminum, in particular to an anticorrosive and anti-oxidation coating material for an electrolytic aluminum anode steel claw and a preparation method thereof.

Background

The electrolytic aluminum production in modern industry mainly adopts cryolite-alumina molten salt electrolytic method, namely: the method is characterized in that a carbon body is used as an anode (the carbon body is connected to one end of a steel claw, the other end of the steel claw is connected with a direct current power supply, so the carbon body is commonly called as an anode steel claw), cryolite in a molten state is used as electrolyte, metal aluminum liquid dissolved in the electrolyte is used as a cathode, direct current is introduced to the two poles, and electrochemical reaction is carried out on the two poles in an electrolytic cell at 950-970 ℃ to obtain a metal aluminum product.

Only the carbon body part in the anode steel claw is contacted with the electrolyte, and the steel claw part above the carbon body is directly exposed in the air above the liquid level of the electrolyte. Since cryolite contains fluorine, HF, hydrogen fluoride, and oxygen are generated in the electrolytic bath at temperatures up to 900 deg.C,CO₂And high-temperature gas mainly including CO gas. The high-temperature gas is corrosive and can cause serious corrosion of the anode steel claw together with oxygen in the air, and corrosion products (mainly iron oxides) of the anode steel claw can enter into the electrolyte and be introduced into an electrolytic aluminum product in production so as to seriously affect the quality of the aluminum product. Meanwhile, the carbon body on the outer surface of the anode steel claw generates a Boolean reaction, so that the carbon body is seriously consumed, and the production cost of the electrolytic aluminum is increased.

Currently, the electrolytic aluminum industry uses a method of applying a protective coating to the anode steel claw to mitigate the above adverse effects of high temperature gases. For example, prior art 1: chinese patent application publication No. CN106634231A discloses an electrolytic aluminum prebaked anode anti-oxidation coating and a preparation method thereof, wherein the anti-oxidation coating is obtained by sintering a ceramic-based continuous phase, a ceramic-based continuous catalytic phase, an alkali and alkaline earth metal auxiliary catalytic phase, a ceramic-based reinforcing phase, a stable phase, a film-forming phase, and a water phase at 500 ℃. However, the oxidation preventing coating needs a catalytic phase, a reinforcing phase, a stabilizing phase and a film forming phase in addition to the ceramic base, and has complicated components and high production cost.

Prior art 2: chinese patent application publication No. CN106189600A discloses a high-temperature-resistant and oxidation-resistant coating for the surface of an electrolytic aluminum carbon anode and a preparation method thereof, wherein the raw materials of the high-temperature-resistant and oxidation-resistant coating comprise alumina sol, acrylic emulsion, boric acid, glycerol, aluminum oxide and water, and the high-temperature-resistant and oxidation-resistant coating can resist high temperature and oxidation of the carbon anode and prevent the carbon anode from being oxidized and peeled off, thereby reducing carbon residue.

Prior art 3: chinese patent application publication No. CN102424730A discloses an antioxidant coating for electrolytic aluminum anode carbon blocks and a preparation method thereof, wherein the coating uses borax or boric acid, kaolin, industrial phosphoric acid, industrial aluminum sulfate and water as raw materials.

Prior art 4: chinese patent application publication No. CN104005056A discloses a method for preparing an electrolytic aluminum carbon anode protective coating, which is prepared by using CA (calcium aluminate) cement as a binder, using waste electrolyte generated in electrolytic aluminum production as refractory aggregate, and adding an additive.

Prior art 5: chinese patent application publication No. CN107057412A discloses a self-curing carbon anode high-temperature oxidation-resistant coating for electrolytic aluminum, which contains hydroxy phosphazene resin, aluminum oxide, aluminum hydroxide, aluminum powder, borax, boron carbide, calcium oxide and organic adhesion promoter.

The formulations of the protective coatings for electrolytic aluminum anodes disclosed above are complex and contain a large amount of other elements in addition to aluminum-containing elements in the raw materials, and although the electrodes can be protected from corrosion, other elements may be introduced into the electrolyte (molten cryolite solution) and may adversely affect the quality of the aluminum product (e.g., other impurities are introduced and the purity of the aluminum product is reduced due to the increased amount of impurities).

In addition, the protective coating formulations for anodes disclosed in the prior art 2-5 all contain organic matters (such as acrylic emulsion and glycerol in the prior art 2; hydroxyl phosphazene resin and organic adhesion promoter in the prior art 5) and/or cement components (such as kaolin in the prior art 3; binder CA (calcium aluminate) cement in the prior art 4), the heat resistance of the organic matters is generally not more than 450 ℃, and the organic matters are easily decomposed and volatilized when heated, so that pore channels are formed in the coating to lose the protective function of the anode steel claw; the cement is a hydraulic adhesive, loses water and loses strength at high temperature, even if the refractory cement cannot withstand the high temperature of more than 900 ℃, the adhesive and the binder lose strength at high temperature, so that the coating is pulverized, the coating can not play a role in effectively protecting the electrode, and the quality of an aluminum product is further deteriorated.

Disclosure of Invention

The invention aims to overcome the technical defects in the prior art, and provides an anticorrosive and anti-oxidation coating material for an electrolytic aluminum anode steel claw, which introduces other elements as little as possible, wherein the raw materials comprise 40-70% of alpha-Al in percentage by mass₂O₃、0-30％γ-Al₂O₃(preferably 5-30%), 2-7% aluminium silicate fibres and 20-30% water glass.

The raw materials are preferablyAccording to the mass percentage, comprises 45-55 percent of alpha-Al₂O₃、15-25％γ-Al₂O₃3-6% of aluminum silicate fiber and 22-27% of water glass.

The raw materials preferably comprise 48 to 52 percent of alpha-Al by weight percentage₂O₃、18-22％γ-Al₂O₃4-6% of aluminum silicate fiber and 24-26% of water glass.

α-Al₂O₃Is in the form of powder, and has a particle size of 150-325 meshes, preferably 200 meshes.

γ-Al₂O₃Is in powder form, and the granularity is less than or equal to 0.043 mm.

The length of the aluminum silicate fiber is less than or equal to 2mm, the diameter of the cross section of the fiber is less than or equal to 0.03mm, and Al in the fiber₂O₃The content is more than 50 percent.

The water glass is in powder form, has particle size of 0.1mm or less, and is selected from sodium water glass and/or potassium water glass, and Na in sodium water glass₂O·nSiO₂Is more than 95 percent. When two types are selected, the mass ratio of the sodium water glass to the potassium water glass is (3-5): 1.

raw material alpha-Al₂O₃、γ-Al₂O₃The water content of the aluminum silicate fiber and the water glass is less than 0.3 wt%.

In a second aspect, the invention provides a preparation method of the anticorrosive and anti-oxidation coating material, which comprises the following steps of mixing alpha-Al in percentage by mass₂O₃、γ-Al₂O₃Weighing the aluminum silicate fibers and the water glass, and then uniformly mixing to obtain the coating material.

The uniform mixing specifically comprises the following steps: after mixing, three samples were taken at different positions of the same batch of coating material, and Al in the samples was analyzed₂O₃Content of (1), Al in any two samples₂O₃The content difference is less than 0.5 percent, namely the mixture is uniformly mixed.

The raw material of the anticorrosive and anti-oxidation coating material for the electrolytic aluminum anode steel claw provided by the invention furthest uses alumina with various crystal forms, and the content of other elements is reduced to the minimum, so that the other elements are prevented from entering into electrolyte (molten cryolite solution), and the quality of an aluminum product is adversely affected. The coating material can form a protective coating on the surface of the anode steel claw, has a compact structure, can reduce the permeation amount of corrosive gas, can obviously reduce the corrosion rate of the electrode, and has strong corrosion resistance and good wear resistance. The ductility of the coating material is enhanced, the coating material is suitable for a high-temperature environment, no reaction or phase change occurs at high temperature, the physicochemical property is stable, the formed coating is not easy to crack and fall off when being used in the high-temperature environment, and at least three periods (one period is formed by one cycle of circulation at the normal temperature of 25 ℃ to 900 ℃ and at the normal temperature of 25 ℃) can be used. The raw materials of the coating material are all solid powder, so that the coating material is convenient to mix uniformly, and the prepared coating material has high yield and stable quality; and the raw materials are convenient to package and transport.

Detailed Description

The anticorrosive antioxidant coating material for the electrolytic aluminum anode steel claw is used for high temperature (about 900 ℃) and contains corrosive gas (HF, CO and CO₂Etc.) and has the performances of common coatings (such as proper viscosity, adhesive force and workability), and high-temperature resistance and corrosion resistance. The function of the coating material is to protect the anode from corrosion so as to prevent corrosion products (ferric oxide) of the anode from entering aluminum liquid of the electrolytic cell and influencing the purity and performance of the electrolytic aluminum product. The iron element mixed in the electrolyte can cause the finally obtained aluminum product to contain Fe, the Fe greatly affects the performance of the aluminum product, such as ductility, brittleness, chemical stability, color of metal, and the like, and the Fe is particularly prevented from being mixed in the production process of industrial aluminum products. Meanwhile, elements in the coating material are prevented from entering aluminum liquid of the electrolytic cell.

The present application is based on these requirements to keep Al as much as possible₂O₃The method is characterized in that the principle that other components which are highest and necessary are not easy to reduce and electrolyze is taken as a principle, a basic formula is originally designed, the basic formula is adjusted through analysis and judgment of possible influences of environmental parameters in an electrolytic cell on the coating, and then the effect of the adjusted formula is repeatedly tested and adjusted in the environment of the electrolytic cell simulated in a laboratory. Finally, the anticorrosive and anti-oxidation coating material for the electrolytic aluminum anode steel claw is determined.

Considering that another important technical problem of the anticorrosion and antioxidation coating material for the electrolytic aluminum anode steel claw is the larger difference of the thermal expansion coefficients between the inorganic coating material and the metal, the thermal expansion coefficient of the coating material made of the conventional inorganic nonmetallic material is about (5-7) multiplied by 10^-6/° C, much lower than the coefficient of thermal expansion (10-20). times.10 of the metal material^-6V. C. This difference in thermal expansion coefficient causes the coating material to crack and peel in the high and low temperature region. Therefore, the invention also adds proper fiber materials into the determined coating material to increase the tensile elongation of the coating material; meanwhile, the adhesive with larger plasticity is selected, so that the coating material has high-temperature flexibility to adapt to thermal expansion and cold contraction of metal.

The anticorrosive and anti-oxidation coating material for the electrolytic aluminum anode steel claw provided by the invention takes various crystal form aluminum oxide products as raw materials to the maximum extent in the composition design, and enables Al in the coating material to be₂O₃The content is maximized, and other elements are prevented from being introduced into the electrolyte, so that the influence of other elements on the quality of the aluminum product is avoided; meanwhile, the coating material can form a protective coating on the surface of the anode steel claw, the coating can effectively protect the electrode from being corroded, and iron elements in the anode steel claw are prevented from entering electrolyte, so that the purity of an aluminum product is improved.

The raw material of the coating material comprises 40-70% of alpha-Al by mass percentage₂O₃、0-30％γ-Al₂O₃(preferably 5-30%), 2-7% of alumina silicate fiber and 20-30% of water glass; preferably, it comprises 55-70% alpha-Al₂O₃、5-15％γ-Al₂O₃3-6% of aluminum silicate fiber and 22-27% of water glass; more preferably, it comprises 60-65% alpha-Al₂O₃、5-10％γ-Al₂O₃4-6% of aluminum silicate fiber and 24-26% of water glass. Wherein the content of the first and second substances,

alpha-Al for use in the invention₂O₃Is in powder form, has particle size of 150-325 mesh (preferably 200 mesh), and contains alpha-Al₂O₃The content is more than 95 percent. alpha-Al₂O₃(a crystal form of alumina) is commonly known as corundum, a type of aluminaThe material, which is calcined warm, has a low water absorption and relatively coarse particle size due to the alpha-Al₂O₃The amount of water required to achieve a certain fluidity is low (less water is used, i.e. the water absorption is low), and the shrinkage during drying (such as high temperature sintering) is low, so that a supporting framework can be formed and the coating can play a supporting role. At the same time, alpha-Al₂O₃Has stable physical and chemical properties, has higher hardness (Mohs hardness of 9), and can improve the corrosion resistance and the wear resistance of the coating. The coating material formulation of the invention maximally assembles alpha-Al in the alumina₂O₃The crystal form is at least 40 wt% and can reach 70 wt% at most.

Gamma-Al used in the present invention₂O₃Is powder with the grain size less than or equal to 0.043mm, gamma-Al₂O₃The content is more than 98 percent, and the aluminum oxide is the same as solute aluminum oxide in the electrolyte and is another crystal form of the aluminum oxide; gamma-Al₂O₃The particles are relatively fine, and the macro performance is relatively soft. Due to alpha-Al₂O₃The particle size of the coating is large, the coating is not compact enough, and the protection effect of the coating on the anode steel claw is poor; therefore, the coating material of the invention is prepared from gamma-Al₂O₃With alpha-Al₂O₃Used in combination with alpha-Al₂O₃To form the skeleton of the coating, using gamma-Al of smaller particle size₂O₃Depopulation of alpha-Al₂O₃The formed framework forms a compact coating on the surface of the anode steel claw, reduces the permeation amount of corrosive gas, and can obviously reduce the corrosion rate of the electrode, thereby better playing the role of protecting the anode steel claw by the coating. The raw material of the coating material of the invention may not contain gamma-Al₂O₃In this case, alpha-Al is ensured₂O₃The particle size of the powder is smaller, which of course leads to a-Al₂O₃The cost of (2) is increased. The invention obtains the gamma-Al in the raw material of the coating material through experimental exploration₂O₃The mass percentage of the coating is 5-30%, and the performance of the coating and the cost of the coating material can be simultaneously considered.

The aluminium silicate fibres used in the invention act as a reinforcement with the aim of improving the resistance of the coating to metalsThe capability of expanding with heat and contracting with cold is fibrous, the fiber length is less than or equal to 2mm, the diameter of the cross section of the fiber is less than or equal to 0.03mm, and Al in the fiber₂O₃The content is more than 50 wt%. The application occasion of the coating material is a high-temperature environment of 900 ℃, the object to be protected is an anode steel claw with metal iron inside, and the thermal expansion coefficient of the metal iron is as high as (10-20) multiplied by 10^-6The thermal expansion coefficient of the conventional inorganic material is not so high, so that the metal iron in the anode steel claw expands when the anode steel claw is used in a high-temperature environment, and a coating containing the inorganic material is cracked and falls off; the aluminum silicate fiber added to the raw material of the coating material of the present invention, preferably Al₂O₃The aluminum silicate fiber with high content, good high temperature resistance and proper fiber thickness (such as glass fiber or ceramic fiber, preferably ceramic fiber, because the ceramic fiber is relatively easy to disperse in the coating material and has the highest performance retention rate after high temperature), can be effectively dispersed in the coating material of the invention, and connects all raw materials into a whole, thereby enhancing the ductility of the coating material and ensuring that the formed coating is not easy to crack and fall off.

The water glass used in the invention is used as an inorganic binder, is powder, is also called water glass powder, has the granularity of less than or equal to 0.1mm, is selected from sodium water glass (sodium silicate) and/or potassium water glass (potassium silicate), is sodium silicate aqueous solution and has the molecular formula of Na₂O·nSiO₂Sodium silicate of Na₂O·nSiO₂More than 95 percent, good high temperature resistance, and the coating material is used as a binder and is suitable for high temperature environment. The potassium silicate glass is potassium silicate water solution with molecular formula of K₂O·nSiO₂K in potassium silicate₂O·nSiO₂Is more than 95 percent. When the water glass is selected from sodium water glass and potassium water glass, the mass ratio of the sodium water glass to the potassium water glass is (3-5): 1 (preferably 4: 1). When sodium silicate in the water glass meets electrolyte, gel breaking is easily generated to cause layered precipitation of the coating and even loss of consolidation capacity, so that the condition of water glass gel breaking caused by the presence of high-valence ions when the viscosity of the water glass is adjusted by the thickening agent (for example, bentonite is used as the thickening agent and gamma-Al₂O₃High-valence ions are ionized easily, and attapulgite is used as a thickening agentContains calcium ions which cause water glass to break gel), and the compounding of a proper amount of potassium silicate and sodium silicate can increase the viscosity of the coating material at high temperature. The water glass can form a glass softening layer at high temperature, so that the coating has plasticity and deformability, and can have the capability of adapting to large expansion coefficient of metal without spalling when being heated when being matched with reinforcing material aluminum silicate fiber; when the temperature is reduced, the glass softening layer is shrunk closely to the steel and is gradually hardened, so that the coating is not peeled off.

On the basis, the invention also provides a method for preparing the anticorrosive and anti-oxidation coating material for the electrolytic aluminum anode steel claw, and the coating material is obtained by weighing the raw materials in percentage by mass and uniformly mixing the raw materials, and is packaged in a moisture-proof and sealed manner for later use. To ensure the uniformity of mixing, 3 samples were taken at different positions (e.g., different depths, different points) of the same batch of coating material after mixing, and Al in the samples was assayed₂O₃Content of (1), Al in any two samples₂O₃The content difference is less than 0.5 percent, namely the mixture is uniformly mixed. Since the coating material of the present invention contains sodium silicate or potassium silicate, the water content of all the raw materials is less than 0.3 wt%.

When in use, the coating material of the invention is added with water and stirred to be mixed, the mass of the water is 30-50 percent (preferably 30-40 percent) of the mass of the coating material, and the coating material is coated or sprayed on electrodes (steel claws and carbon blocks) to form the anticorrosive and anti-oxidation coating for the electrolytic aluminum anode steel claws.

The present invention will be described more specifically and further illustrated with reference to specific examples, which are by no means intended to limit the scope of the present invention.

The raw materials used in the coating material of the present invention are all commercially available.

Example 1

The coating material of the embodiment comprises 50% of alpha-Al by mass₂O₃、20％γ-Al₂O₃5% of aluminum silicate fiber and 25% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 1, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 1, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic bath for electrolytic aluminum.

The control is an anode steel claw without any coating and is arranged in an electrolytic cell for electrolyzing aluminum.

An electrolytic aluminum sample was taken as a test sample I in the electrolytic bath for coating material sample 1, and an electrolytic aluminum sample was taken as a comparative sample in the electrolytic bath for mounting the comparative sample.

Analysis of Fe in two electrolytic aluminum products of test sample I and comparative sample₂O₃Content and total amount of impurities, and the result shows that: fe in test sample I₂O₃55% lower than that in the comparative sample, and the total amount of impurities in the test sample I is 25% lower than that in the comparative sample. Due to Fe₂O₃The content and the total amount of impurities may be influenced by other factors than the coating (e.g. the raw material itself contains Fe₂O₃And Fe in different batches of raw materials₂O₃Different in content) and therefore the relative reduction is used as an evaluation parameter, the experimental procedure is described with reference to example 4, and the detection data has been converted into the relative reduction.

Example 2

The coating material of the embodiment comprises 65% of alpha-Al by mass₂O₃、5％γ-Al₂O₃7% of aluminum silicate fiber and 23% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 2, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 2, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying), naturally drying for 12 hours to form a coating on an anode steel claw, and installing the coating on an electrolytic cell to electrolyze aluminum.

The same is used for comparison as in example 1.

An electrolytic aluminum sample was taken as a test sample II in the electrolytic bath for coating material sample 2, and an electrolytic aluminum sample was taken as a comparative sample in the electrolytic bath for mounting the comparative sample.

Analysis of Fe in two electrolytic aluminum products for test sample II and comparative sample₂O₃Content and total amount of impurities, and the result shows that: fe in test sample II₂O₃The amount of the impurities in the test sample II is reduced by 45% compared with the control sample and by 25% compared with the control sample (please refer to the description of example 4, the test data is converted into relative reduction amount).

Example 3

The coating material of the embodiment comprises 40% of alpha-Al by mass₂O₃、30％γ-Al₂O₃7% of aluminum silicate fiber and 23% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 3, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 3, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic cell for electrolytic aluminum.

The same is used for comparison as in example 1.

An electrolytic aluminum sample was taken as a test sample III in the electrolytic bath for coating material sample 3, and an electrolytic aluminum sample was taken as a comparative sample in the electrolytic bath for mounting the comparative sample.

Analysis of Fe in two electrolytic aluminium products of test sample III and comparative sample₂O₃Content and total amount of impurities, and the result shows that: fe in test sample III₂O₃The total amount of impurities in test sample III was reduced by 43% compared to the control sample and by 20% compared to the control sample (see example 4 for the experimental procedure, the data are converted to relative reductions).

Example 4

The coating material of the present example comprises, in mass percent, 63% of α -Al₂O₃、7％γ-Al₂O₃5% of aluminum silicate fiber, 20% of sodium silicate and 5% of potassium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 4, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 4, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying), naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic cell for electrolytic aluminum.

The same is used for comparison as in example 1.

An electrolytic aluminum sample was taken as a test sample IV in the electrolytic bath for coating the coating material sample 4, and an electrolytic aluminum sample was taken as a comparative sample in the electrolytic bath for mounting the comparative sample.

Analysis of Fe in two electrolytic aluminum products of test sample IV and comparative sample₂O₃Content and total amount of impurities, results Fe in test sample IV₂O₃The average reduction in the sample is 42%, and the total amount of impurities is 30%. The experimental procedure was as follows:

the experimental method comprises the following steps: detecting the content of each element in the coating material; then coating the coating material on the anode steel claw to form a coating, and installing the steel claw into an electrolytic bath to carry out electrolytic aluminum production; and finally, taking an electrolytic aluminum sample to analyze the content of each element in the electrolytic aluminum product.

The experimental results are as follows: the coating material of example 4 was tested for the elemental content of 6 parallel samples (see samples 4-1 through 4-6 in table 1), and the elemental content of each of the coating materials is shown in table 1.

Table 1 example 4 content of each element (%)

Sample(s)	Al2O3	Fe2O3	SiO2	K2O	Na2O
						Sample 4-1	72.50	0.066	20.46	1.51	4.89
Sample 4-2	73.12	0.057	19.89	1.49	4.91
						Samples 4-3	72.48	0.070	20.25	3.01	3.74
Samples 4-4	72.45	0.056	20.33	2.69	3.81
						Samples 4 to 5	72.49	0.064	20.29	1.48	4.99
Samples 4 to 6	72.43	0.061	20.73	1.49	3.92

Table 1 shows that the coating material of example 4 has high alumina content and contains as few other elements as possible, so as to ensure that iron oxide on the steel claw does not enter the electrolytic aluminum liquid, and the elements in the coating material also enter the electrolytic aluminum liquid as little as possible, so that even if a small amount of coating material ingredients enter the electrolytic aluminum liquid, the electrolytic aluminum product is not polluted seriously.

Selecting a plurality of electrolytic cells of a plurality of electrolytic aluminum production enterprises, selecting two anode steel claws with the same specification parameters in each electrolytic cell, respectively coating the coating material of the sample 4-1 on one anode steel claw in each electrolytic cell (the number is respectively from back-01 to back-10), and respectively coating the number of the other uncoated anode steel claw in each electrolytic cell from front-01 to front-10; the electrolytic aluminum is produced by using the anode steel claw, and the content of each element in the obtained electrolytic aluminum product is shown in table 2.

TABLE 2 electrolytic aluminum product for each element content (%)

Steel claw numbering	Fe	Si	K	Na	Al	Total amount of impurities
							Front-01	0.21	0.09	0.0021	0.0015	99.67	0.33
Rear-01	0.095	0.12	0.0020	0.0017	99.76	0.24
							Front-02	0.20	0.08	0.0012	0.0015	99.68	0.32
Rear-02	0.11	0.09	0.0013	0.0014	99.77	0.23
							Front-03	0.11	0.08	0.0011	0.0010	99.77	0.23
Rear-03	0.063	0.08	0.0010	0.0011	99.85	0.15
							Front-04	0.10	0.08	0.0012	0.0011	99.76	0.24
Rear-04	0.060	0.09	0.0013	0.0012	99.83	0.17
							Front-05	0.23	0.08	0.0011	0.0010	99.64	0.36
Rear-05	0.13	0.09	0.0013	0.0011	99.74	0.26
							Front-06	0.20	0.09	0.0012	0.0013	99.69	0.31
Rear-06	0.13	0.10	0.0015	0.0016	99.77	0.23
							Front-07	0.22	0.07	0.0011	0.0015	99.62	0.38
Rear-07	0.13	0.09	0.0012	0.0015	99.74	0.26
							Front-08	0.19	0.08	0.0012	0.0011	99.68	0.32
Rear-08	0.10	0.07	0.0011	0.0014	99.78	0.22
							Front-09	0.10	0.06	0.0013	0.0016	99.77	0.23
Rear-09	0.071	0.06	0.0011	0.0016	99.85	0.15
							Front-10	0.11	0.06	0.0010	0.0014	99.76	0.24
Rear-10	0.066	0.06	0.0011	0.0012	99.83	0.17

As can be seen in table 2: the aluminum content of the electrolytic aluminum product, the experimental samples using the coating material of example 4 (labeled "after") was higher than the comparative samples without coating (labeled "before"), the Al content was above 99.74%; the Fe content in the experimental sample is greatly reduced compared with that of a comparative sample, the highest Fe content is reduced by 55 percent (such as a No. 01 steel claw), and the absolute content is not more than 0.13 percent; the total impurity content (calculated according to 100 percent to Al percent) of the experimental sample is not higher than 0.26 percent, and is greatly reduced compared with a comparative sample, and the maximum impurity content is reduced by 35 percent (such as No. 03 and No. 09 steel claws).

And (3) detecting the performance of the coating:

the coating materials of examples 1-4 were tested for parameters using established architectural coating testing methods to assess whether they qualify as coatings. Wherein, the washing resistance is carried out according to a washing test machine and a test operation procedure specified by 3.1 and 5.2 in GB/T9266; the surface dry time performance is carried out according to the regulation of a method B in GB/T1728; the initial dry cracking resistance was carried out according to the method specified in GB/T9779 under 5.6; the bonding strength performance is carried out according to the method specified in GB/T9779-2005 5.7; the water vapor transmission rate was determined in accordance with the method specified in JG/T309 as 7.2. The results of these tests show that the coating materials of examples 1 to 4, as coating materials, meet the requirements of the corresponding standards with respect to brushing resistance, open time, initial drying crack resistance, adhesive strength and water vapor transmission rate.

Comparative example 1

The raw material of the coating material comprises 75 percent of alpha-Al by mass percentage₂O₃、5％γ-Al₂O₃7% of aluminum silicate fiber and 13% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 4, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 4, mechanically stirring for 5 minutes, uniformly coating the electrolytic aluminum anode with a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours to form a coating on an anode steel claw, and enabling other objects to have powder falling when touching the coating, namely, the pulverization phenomenon is serious and electrolytic aluminum cannot be carried out.

Comparative example 2

The raw material of the coating material comprises 30 percent of alpha-Al by mass percentage₂O₃、40％γ-Al₂O₃5% of aluminum silicate fiber and 25% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 5, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 5, mechanically stirring for 5 minutes, uniformly coating the electrolytic aluminum anode by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours to form a coating on an anode steel claw, wherein the obtained coating has a shrinkage cracking phenomenon and cannot carry out electrolytic aluminum.

Comparative example 3

The raw material of the coating material comprises 40 percent of alpha-Al by mass percentage₂O₃、35％γ-Al₂O₃5% of aluminum silicate fiber and 20% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 6, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 6, mechanically stirring for 5 minutes, uniformly coating the electrolytic aluminum anode by adopting a blade coating mode (or spraying), naturally drying for 12 hours to form a coating on an anode steel claw, and enabling the obtained coating to crack, so that the electrolytic aluminum cannot be carried out.

Comparative example 4

The raw material of the coating material comprises 42 percent of alpha-Al by mass percentage₂O₃、30％γ-Al₂O₃1% of aluminum silicate fiber and 27% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 7, adding room-temperature tap water accounting for 45 wt% of the mass of the coating material sample 7, mechanically stirring for 5 minutes, uniformly coating over 1mm on an electrolytic aluminum anode in a blade coating mode (or spraying), naturally drying for 12 hours to form a coating on an anode steel claw, installing the coating in an electrolytic cell for electrolytic aluminum, and cracking and dropping the coating at high temperature in the electrolytic process.

Comparative example 5

The raw material of the coating material comprises 40 percent of alpha-Al by mass percentage₂O₃、30％γ-Al₂O₃10% of aluminum silicate fiber and 20% of sodium silicate.

The raw materials are weighed according to the content and are uniformly mixed to produce a coating material sample 8, room-temperature tap water with the mass of 8 wt% of the coating material sample is added, the mechanical stirring is carried out for 5 minutes, and the raw materials cannot be uniformly dispersed and cannot be subjected to subsequent blade coating or spraying.

Comparative example 6

The raw material of the coating material comprises 48 percent of alpha-Al by mass percentage₂O₃、30％γ-Al₂O₃7% of aluminum silicate fiber and 15% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 9, adding room-temperature tap water accounting for 45 wt% of the mass of the coating material sample 9, mechanically stirring for 5 minutes, uniformly coating the electrolytic aluminum anode by adopting a blade coating mode (or spraying), naturally drying for 12 hours to form a coating on an anode steel claw, and enabling other objects to have powder falling when the coating touches the coating, namely the pulverization phenomenon is serious.

Comparative example 7

The raw material of the coating material comprises 35 percent of alpha-Al by mass percentage₂O₃、25％γ-Al₂O₃7% of aluminum silicate fiber and 35% of sodium silicate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 10, adding room-temperature tap water accounting for 45 wt% of the mass of the coating material sample 10, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic cell for electrolytic aluminum.

According to the test in example 3, the total amount of impurities in the electrolytic aluminum sample obtained by the coating material sample 10 was increased by 2.5% from that in the test sample III obtained in example 3.

Comparative example 8

The raw material of the coating material comprises 50 percent of alpha-Al by mass percentage₂O₃、20％γ-Al₂O₃5% of aluminum silicate fiber and 25% of refractory cement.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 11, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 11, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic bath for electrolytic aluminum.

Refractory cement is a common inorganic binder, is mainly used for amorphous refractory materials, and is often used in kiln repair (such as preparation of refractory mortar for spraying on a kiln). In the comparative example, the refractory cement is used as a binder in the coating material instead of water glass, and when the coating is formed on the anode steel claw and is used for electrolytic aluminum, the coating is pulverized mainly because the refractory cement is dehydrated at about 300 ℃ and is dehydrated and pulverized in the environment of the temperature (900 ℃) for producing the electrolytic aluminum.

Comparative example 9

The raw material of the coating material comprises 50 percent of alpha-Al by mass percentage₂O₃、15％γ-Al₂O₃5% of aluminum silicate fiber and 30% of aluminum dihydrogen phosphate.

Weighing the raw materials according to the content, uniformly mixing to produce a coating material sample 12, adding room-temperature tap water accounting for 33 wt% of the mass of the coating material sample 12, mechanically stirring for 5 minutes, uniformly coating the anode of the electrolytic aluminum by adopting a blade coating mode (or spraying) for more than 1mm, naturally drying for 12 hours, forming a coating on an anode steel claw, and installing the anode steel claw into an electrolytic bath for electrolytic aluminum.

Aluminum dihydrogen phosphate is a common high-temperature binder and is widely used for repairing refractory materials. This comparative example replaces water glass with aluminium dihydrogen phosphate as the binder in the coating material. Aluminum dihydrogen phosphate is used as a binder, has outstanding high-temperature performance, can resist higher temperature than water glass, but is different from the water glass in that the aluminum dihydrogen phosphate is crystalline after dehydration, has strong coating rigidity and is difficult to adapt to the larger thermal expansion rate of steel materials at high temperature, so that the prepared coating is easy to crack and fall off at high temperature in the electrolytic process and cannot be repeatedly used.

As is clear from the comparison of examples with comparative examples 8 to 9, water glass is a relatively preferable binder. The water glass is amorphous, has no fixed melting point, and is a high-temperature softening process at the high temperature of the electrolytic process, and the softening process is favorable for matching the large expansion coefficient of the steel, so that the integrity of the coating is kept.

The content of each raw material of the coating material is not independent from each other, but is complementary; such as alpha-Al₂O₃Too low of (A) means that the content of other raw materials is increased, for example, by increasing the content of gamma-Al₂O₃In order to compensate for alpha-Al₂O₃Due to the reduced content of gamma-Al₂O₃The particle size of (A) is fine, and the formed coating is easy to crack due to the high content of (A); or increasing the content of aluminum silicate fiber to compensate for alpha-Al₂O₃The content of the aluminum silicate fiber is reduced, and the fiber can cause that other raw materials can not be uniformly dispersed and can not form a uniform coating material; or increasing the content of sodium silicate to compensate for alpha-Al₂O₃The content of the sodium silicate is reduced, and the sodium silicate is water-soluble, so that the content of the sodium silicate in the coating material is too high, and when the coating is prepared by adding water, the obtained coating has increased fluidity, flows on the anode steel claw and cannot be adhered to the anode steel claw, so that a uniform coating cannot be formed on the anode steel claw. If alpha-Al is present₂O₃Is too high, the content of other raw materials is reduced, for example, gamma-Al is reduced₂O₃In the content of (A), alpha-Al is required₂O₃Particle size of (a) is reduced, and alpha-Al₂O₃The hardness is high, the grinding difficulty and the cost are very high, and the method cannot be suitable for industrial production; or the content of the aluminum silicate fiber is reduced, and the prepared coating has poor ductility and can not adapt to cracking and falling off of the metal iron in the anode steel claw when being used at high temperature; or the content of sodium silicate is reduced, the sodium silicate is used as a binder, and the coating prepared by using the sodium silicate with too low content has serious powder falling phenomenon, so that the protective effect on the anode steel claw cannot be exerted. Likewise, the content of other raw materials is increased or decreased, resulting in alpha-Al₂O₃Too low or too high a content of (b) makes the prepared coating easily crack or have a dusting phenomenon.

In conclusion, the coating material has good construction performance, excellent adhesion capability and outstanding high-temperature performance in the using process; compared with the method without using the coating material, the coating material is applied to the production of electrolytic aluminum, the Fe content in the electrolytic aluminum product is reduced by more than 40 percent, the total impurity content is reduced by more than 20 percent, the quality of the aluminum product is improved by one brand, and the selling price can be improved by 30-50 yuan/ton. The selling price of the aluminum product is increased by 30-50 yuan/ton and the income can reach 1500-; after the coating material is used, the maintenance cost of the anode can be saved by 386 ten thousand yuan per year, and remarkable economic benefit is brought.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the content of the present invention.